Tributes were paid to Lady Thatcher, with the Queen said to be "sad" at the news of the death, while Prime Minister David Cameron called her a "great leader" and a "great Briton".

Former Labour Prime Minister Tony Blair said Lady Thatcher was "a towering political figure" who had a vast global impact.

Margaret Thatcher was a towering political figure.

Very few leaders get to change not only the political landscape of their country but of the world. Margaret was such a leader. Her global impact was vast.

And some of the changes she made in Britain were, in certain respects at least, retained by the 1997 Labour Government, and came to be implemented by governments around the world.

As a person she was kind and generous spirited and was always immensely supportive to me as Prime Minister although we came from opposite sides of politics.

Even if you disagreed with her as I did on certain issues and occasionally strongly, you could not disrespect her character or her contribution to Britain’s national life.

She will be sadly missed.

– Tony Blair

Current Labour leader Ed Miliband said she had "moved the centre ground of British politics" and called her "an extraordinary politician and unique political figure."

Sir John Major told ITV News that his predecessor was the "right politician for the time" and said "she had a clear view of what was necessary."

Global leaders also paid tribute to the Iron Lady, with US President Barack Obama calling her a "true friend" to the US.

With the passing of Baroness Margaret Thatcher, the world has lost one of the great champions of freedom and liberty, and America has lost a true friend.

As a grocer’s daughter who rose to become Britain’s first female prime minister, she stands as an example to our daughters that there is no glass ceiling that can’t be shattered.

As prime minister, she helped restore the confidence and pride that has always been the hallmark of Britain at its best.

And as an unapologetic supporter of our transatlantic alliance, she knew that with strength and resolve we could win the Cold War and extend freedom’s promise.

Here in America, many of us will never forget her standing shoulder to shoulder with President Reagan, reminding the world that we are not simply carried along by the currents of history—we can shape them with moral conviction, unyielding courage and iron will.

Michelle and I send our thoughts to the Thatcher family and all the British people as we carry on the work to which she dedicated her life—free peoples standing together, determined to write our own destiny.

– US President Barack Obama

Reformist Soviet leader Mikhail Gorbachev described the former prime minister as a "heavyweight politician", while Nancy Reagan, the wife of former US President Ronald, said the world owed Lady Thatcher "a debt of gratitude."

Margaret Thatcher with Nancy Reagan. Credit: Fiona Hanson/PA Archive

The former Tory leader was also widely condemned by those on the Left, with ex-London Mayor and Labour MP Ken Livingstone criticising her legacy.

She created today's housing crisis, she produced the banking crisis, she created the benefits crisis ... Every real problem we face today is the legacy of the fact she was fundamentally wrong.

– KEN LIVINGSTONE ON SKY NEWS

Singer Morrissey said Lady Thatcher was "a terror without an atom of humanity" and that "she destroyed the British manufacturing industry, she hated the miners, she hated the arts, she hated the Irish Freedom Fighters and allowed them to die".

Next week the streets will be cleared for a procession from Westminster to St Paul's, where there will be a televised service attended by dignitaries from around the world. The day has yet to be confirmed.

Tributes to the late Margaret Thatcher outside her home in London. Credit: Suzan/EMPICS Entertainment

Lady Thatcher's frail condition - especially after the death of husband, Denis, in 2003 - led to frequent bouts of speculation about her health.

However, friends who saw her regularly said she remained alert and interested in politics until recently.

She was said to be delighted Mr Cameron, and before him, Gordon Brown extended invitations to visit 10 Downing Street and Chequers.